Brad, your problem has several causes. The first is probably subconscious -- you sense which keg is nearing the end, so you avoid it in favor of the others. Eventually they get even lower than the one you're avoiding, which causes you to sense that the first has more, so you start drinking that one again. That continues until you're blowing foam out of all three at once. The second is your lack of cornies. No self-respecting brewer gets by with three or four kegs. Order more, man!!!
I haven't run out of beer, either bottled or kegged, in about four years, since I went all grain. Yesterday I transferred three beers to cornies, and they will soon join the two that are already in my fridge/freezer -- next to the five or six cases of bottles.
Brew On!